A linear guide unit of this kind, known as a gantry module, is produced by Afag AG, a company specializing in automated manufacturing technology in Menziken (CH).
The disadvantage in the known gantry modules is that each guide rail is only affixed to the guide support frictionally. The guide rails are attached to the guide support by means of screws; the screws press a support surface of the respective guide rails against a counterpart support surface of the guide support with a predetermined contact force. The intensity of the contact force determines the amount of frictional force preventing the guide rail from shifting in the lateral direction, which lateral direction lies in a contact plane orthogonal to a lifting direction of the guide rail away from the guide support, between the support surface and the counterpart support surface, and is oriented orthogonal to the guide direction. It is therefore clearly evident that the lateral forces that can be absorbed by each guide rail are merely a fraction of the contact forces exerted by the fastening screws of the respective guide rail.
In the known gantry axis, the two guide rails are rotated in relation to each other by 90° around a rotation axis parallel to the guide direction. It is therefore possible to attach loads to two fastening surfaces orthogonal to each other on a moving load carrier of the known gantry axis; a guide rail and a sliding carriage guided on it is continuously acted on by an applied load. But the above-mentioned lateral forces still act on the respective other guide rail with a force component orthogonal to the guide direction and orthogonal to the lifting direction of the respective guide rail away from the guide support.